1. Field of the Invention
The present invention relates to welding apparatuses using induction heating, wherein work pieces to be welded are previously positioned for welding. More particularly, the invention relates to apparatuses for hard facing of valves for internal combustion engines by melting rings of heat-resistant alloys upon the working surface of the valves.
The term "working surface" is used to denote a chamfer made in the valve head of an internal combustion engine and adapted to provide for a close fitting between the valve and the respective seat chamfer.
Most efficiently the invention can be employed at enterprises engaged in serial production of valves for internal combustion engines.
2. Description of the Prior Art
It is known that to effect hard facing of a valve, an alloy ring is set on the head thereof, the valve is put in a vertical position and the valve head with the ring set thereupon is placed into a high-temperature heater, for instance in a high-frequency inductor.
At present, valves are hard-faced with the aid of devices wherein fitting a ring onto the valve head, positioning the valve in a vertical alignment and feeding the valve into the inductor are effected by mechanical means, for instance a manipulator.
Despite the automation of the hard facing process, there still remain possibilites to increase the efficiency of the above devices by shortening the time for assembling the work valve with the ring, as well as by carrying out the above assembling at a time when the previous valve is being treated.
Known in the art is an apparatus, for hard facing of valves for internal combustion engines, having an assembling means (for fitting the ring onto the valve) made in the form of a vertically positioned tubular body adjoined by gravity feed trays for feeding the work valves and the rings to be melted to the tubular body.
Assembling the work valve with the ring is effected in the above apparatus by gravity. Hence, the means is simple in design and more efficient as compared with similar means wherein the assembling is performed by a number of mechanisms.
Despite obvious advantages, said means is not reliable enough in operation because sometimes the ring may fall wide of the valve stem, or else the valve itself falls at a moment when it is being placed under the inductor. Naturally, it requires constant control and interference on the part of the operator.
Also known in the art is an apparatus for hard facing of valves for internal combustion engines comprising a means for assembling the work valve with the ring to be melted (cf. Laid-open Swedish Application No. 7802954-3; British Pat. No. 1,574,295), comprising a vertically positioned tubular body adjoined by gravity feed trays, for feeding the work valves and the rings respectively, a receiver for receiving the ring and putting it into the valve stem, located under the tray for feeding the valves and intended for positioning the valve so that its stem is directed upward, and a pusher located under the tubular body and adapted for feeding the valve with the ring fitted upon its head into the inductor, and a mechanism for holding the valve therein.
For placing the valves inside the tubular body, in the wall thereof there is provided a hole adjoined by the tray for feeding the rings to be melted; the receiver for receiving the rings is a plate inserted into the slot provided in the tubular body below the hole for placing the rings therein. The curtain is connected with a drive providing for its reciprocating movement.
The pusher for feeding the rings is mounted on a slide and has a socket to accommodate the valve with the ring put thereupon, the pusher slide being connected with a reciprocating drive for alternately placing the pusher under the tubular body or the inductor.
The tray for feeding the rings has a complicated form providing for a vertical position of the rings at the entry side of the tray and a horizontal position at the exit side thereof. A separator for feeding the rings by the piece from a storage is mounted at the entry side of the ring feeding tray.
To feed the rings with a right side turned in the direction of movement, i.e., to prevent the ring from turning over, there is provided another plate inserted into the slot made in the tubular body above the aforementioned hole.
Despite the reliability achieved, the complicated form of the tray for feeding the rings, the arrangement of the pusher on the slide connected with drives, and the necessity of machining the tubular body to have various entries and exits for the valves and rings complicate the design and hence the manufacturing process of the above apparatus.
In addition, the time required for moving the pusher under the heater and then back under the tubular body restricts the efficiency of the above apparatus.